Question on this.... What then stops the NN Parks Dept from promulgating rules prohibiting firearms from parks.... since they are an Agency and not a "municipal subdivision?"
Very short answer - they are a sub-division of the City of Newport News. Which means they are in fact a "municipal subdivision".
A rough way to determine if the entity is a municipal subdivision or a state agency is to see who has the authority to appoint/fire the head officer. If the Governor can hire/fire, directly or through one of his Secretaries, then it is a state agency. If the Mayor/Board of Supervisors hires/fires then it is some lesser part of a municipality. (There are some finer points, but that shuld do for 99 44/100 of cases.)
stay safe.